Re: [PATCH v3 1/4] dt-bindings: mfd: Add bindings for Ampere Altra SMPro drivers

[Quan Nguyen <quan@os.amperecomputing.com>]

On 14/04/2021 15:28, Quan Nguyen wrote:
> On 13/04/2021 20:49, Rob Herring wrote:
>> On Fri, Apr 09, 2021 at 10:13:29AM +0700, Quan Nguyen wrote:
>>> Adds device tree bindings for SMPro drivers found on the Mt.Jade 
>>> hardware
>>> reference platform with Ampere's Altra Processor family.
>>>
>>> Signed-off-by: Quan Nguyen <quan@os.amperecomputing.com>
>>> ---
>>>   .../bindings/hwmon/ampere,ac01-hwmon.yaml     |  28 +++++
>>>   .../devicetree/bindings/mfd/ampere,smpro.yaml | 105 ++++++++++++++++++
>>>   2 files changed, 133 insertions(+)
>>>   create mode 100644 
>>> Documentation/devicetree/bindings/hwmon/ampere,ac01-hwmon.yaml
>>>   create mode 100644 
>>> Documentation/devicetree/bindings/mfd/ampere,smpro.yaml
>>>
>>> diff --git 
>>> a/Documentation/devicetree/bindings/hwmon/ampere,ac01-hwmon.yaml 
>>> b/Documentation/devicetree/bindings/hwmon/ampere,ac01-hwmon.yaml
>>> new file mode 100644
>>> index 000000000000..fbf7ec754160
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/hwmon/ampere,ac01-hwmon.yaml
>>> @@ -0,0 +1,28 @@
>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/hwmon/ampere,ac01-hwmon.yaml#
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: Hardware monitoring driver for the Ampere Altra SMPro
>>> +
>>> +maintainers:
>>> +  - Quan Nguyen <quan@os.amperecomputing.com>
>>> +
>>> +description: |
>>> +  This module is part of the Ampere Altra SMPro multi-function 
>>> device. For more
>>> +  details see ../mfd/ampere,smpro.yaml.
>>> +
>>> +properties:
>>> +  compatible:
>>> +    enum:
>>> +      - ampere,ac01-hwmon
>>> +
>>> +  reg:
>>> +    maxItems: 1
>>> +
>>> +required:
>>> +  - compatible
>>> +  - reg
>>> +
>>> +additionalProperties: false
>>> diff --git a/Documentation/devicetree/bindings/mfd/ampere,smpro.yaml 
>>> b/Documentation/devicetree/bindings/mfd/ampere,smpro.yaml
>>> new file mode 100644
>>> index 000000000000..5613c420869e
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/mfd/ampere,smpro.yaml
>>> @@ -0,0 +1,105 @@
>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/mfd/ampere,smpro.yaml#
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: Ampere Altra SMPro firmware driver
>>> +
>>> +maintainers:
>>> +  - Quan Nguyen <quan@os.amperecomputing.com>
>>> +
>>> +description: |
>>> +  Ampere Altra SMPro firmware may contain different blocks like 
>>> hardware
>>> +  monitoring, error monitoring and other miscellaneous features.
>>> +
>>> +properties:
>>> +  compatible:
>>> +    enum:
>>> +      - ampere,smpro
>>
>> Again, not very specific. There's only 1 version of 'smpro' h/w or
>> firmware? Are the firmware version and features discoverable? If not,
>> you need to be more specific (or better yet, make them discoverable).
>>
> Hi Rob,
> 
> So far, there's nothing to guarantee this is the only version of SMPro 
> and neither firmware version nor features that are discoverable.
> 
> In fact, it was "ampere,ac01-smpro" specifically in my v1. But this is 
> the "ampere,smpro" in arch/arm/boot/dts/nuvoton-npcm730-kudo.dts, that 
> is why it got changed to "ampere,smpro" to avoid changes in that dts file.
> 
> I'm thinking about change it back to "ampere,ac01-smpro" in next version 
> to make this compatible string more specific.
> 

Hi Rob, I have a second thought on this.

What MFD SMPro driver does is only to expose the register map for child 
drivers to use. Child drivers are capable to handle the specific details 
among SMPro version if necessary. Hence, even though we address the 
SMPro specific here (ie: by using specific compatible string), 
eventually, regardless of any version the SMPro might be, the MFD SMPro 
driver still just to expose the register map for its child drivers.

So, if that makes sense, I'd like to keep the "ampere,smpro" as 
compatible string.

- Quan

>>> +
>>> +  reg:
>>> +    description:
>>> +      I2C device address.
>>> +    maxItems: 1
>>> +
>>> +  "#address-cells":
>>> +    const: 1
>>> +
>>> +  "#size-cells":
>>> +    const: 0
>>> +
>>> +patternProperties:
>>> +  "^hwmon(@[0-9a-f]+)?$":
>>> +    $ref: ../hwmon/ampere,ac01-hwmon.yaml
>>> +
>>> +  "^misc(@[0-9a-f]+)?$":
>>
>> You don't need these child nodes in DT if there are no resources
>> associated with them. The parent driver can instantiate all the
>> sub-functions.
>>
> 
>  From v3, there is a "reg" property introduced for the child driver, 
> especially for the misc driver. This is unavoidable because other 
> properties might be introduced in future for other misc features.
> 
>>> +    type: object
>>> +    description: |
>>> +      This module is part of the Ampere Altra SMPro multi-function 
>>> device
>>> +      to support miscellaneous features
>>> +    properties:
>>> +      compatible:
>>> +        enum:
>>> +          - ampere,ac01-misc
>>> +      reg:
>>> +        maxItems: 1
>>> +
>>> +    required:
>>> +      - compatible
>>> +      - reg
>>> +
>>> +  "^errmon(@[0-9a-f]+)?$":
>>> +    type: object
>>> +    description: |
>>> +      This module is part of the Ampere Altra SMPro multi-function 
>>> device
>>> +      that supports error monitoring feature.
>>> +
>>> +    properties:
>>> +      compatible:
>>> +        enum:
>>> +          - ampere,ac01-errmon
>>> +      reg:
>>> +        maxItems: 1
>>> +
>>> +    required:
>>> +      - compatible
>>> +      - reg
>>> +
>>> +required:
>>> +  - "#address-cells"
>>> +  - "#size-cells"
>>> +  - compatible
>>> +  - reg
>>> +
>>> +additionalProperties: false
>>> +
>>> +examples:
>>> +  - |
>>> +    i2c {
>>> +        #address-cells = <1>;
>>> +        #size-cells = <0>;
>>> +
>>> +        smpro@4f {
>>> +            compatible = "ampere,smpro";
>>> +            reg = <0x4f>;
>>> +            #address-cells = <1>;
>>> +            #size-cells = <0>;
>>> +
>>> +            hwmon@10 {
>>> +                compatible = "ampere,ac01-hwmon";
>>> +                reg = <0x10>;
>>> +            };
>>> +
>>> +            misc@b0 {
>>> +                compatible = "ampere,ac01-misc";
>>> +                reg = <0xb0>;
>>> +            };
>>> +
>>> +            errmon@80 {
>>> +                compatible = "ampere,ac01-errmon";
>>> +                reg = <0x80>;
>>> +            };
>>> +
>>> +        };
>>> +    };
>>> -- 
>>> 2.28.0
>>>
>